Experimental study of instrumented fully grouted rock bolts subjected to pull load

Rebar-type rock bolts sized 22 mm in diameter and 600 mm in length become equipped with four resistance strain gauges placed along their length. A total of 450 mm bolt lengths is inserted in resin grouted inside a cement mortar cast cylindrical sample with a diameter of 250 mm. Strain gauges are affixed to the rod's surface at four distinct points. The diameter of the hole is adjusted to 32 mm, 36 mm, and 42 mm. The embedded bolt cement mortar samples are positioned in a pull-testing machine and securely affixed to the frame using tie rods. The rod is subjected to three distinct loading rates. This paper examines load-deformation relationship curves for various hole sizes during pulling to assess peak bond strength and stiffness differences. The tensile strains measured at four places are corroborated with an analytical equation presented in this research.